A week of cocktails on a cruise ship can quietly double your holiday budget. That's why nearly every big mass-market cruise line sells flat-fee drink packages — and why choosing wisely (or skipping one) matters. The Points Guy has pulled together a line-by-line breakdown of what's on offer, and the takeaway is simple: the maths only works for certain drinkers.

The basics first. A drink package lets you order drinks — anything from sodas to cocktails, wine by the glass and specialty coffee, depending on the tier — for one daily rate. Most lines sell a cheaper non-alcoholic tier too, often under $12 per day for sodas, while full alcohol packages range widely. Carnival, Norwegian, MSC and Holland America charge roughly $29 to $95 per person per day for their most inclusive plans; Royal Caribbean and Celebrity can top $100.

A few quirks catch people out. On Carnival, Holland America and MSC, if one adult in a cabin buys the package, every adult in that cabin must buy it too — a deliberate anti-sharing rule. Princess and Windstar are the notable exceptions, though technically you still can't buy rounds for friends. 'Unlimited' isn't always unlimited either: Carnival, MSC and Holland America cap alcoholic drinks at 15 per person per day, which is generous but a cap nonetheless. Most packages work in bars, lounges and eateries, but not room service or minibars, and some exclude private islands (Celebration Key and Half Moon Cay, for example, aren't covered on Carnival).

The headline packages: Carnival's Cheers! program runs $74.95 per day on board, or $69.95 pre-purchased, covering drinks up to $20 with a 15-drink daily limit. Celebrity's Premium Drink Package starts at $100 per day and covers drinks up to $19 — though anyone staying in The Retreat gets it free. Holland America's Elite Beverage Package is $60.95 plus 20% gratuity, with a $16 per-drink ceiling. MSC's Premium Extra Package starts at $50 per day pre-booked on longer sailings (rising to $82 on board) and, unusually, works on the line's private island, Ocean Cay. Norwegian's Free at Sea package is among the cheapest, at $28.50 to $32 per day depending on cruise length.

Disney Cruise Line and Virgin Voyages are the odd ones out — neither sells a traditional alcohol package, though both have other ways to cut beverage costs.

So is it worth it? Do the sums before you sail. If you'll genuinely order five or six $10-plus drinks a day plus coffees and bottled water, a $60-70 package pays off. If you're a couple-of-glasses-of-wine person, you'll likely lose money — and nobody should spend a holiday drinking to 'break even'. Non-drinkers aren't forgotten: alcohol-free tiers like Carnival's Zero-Proof Package (from $29.95) or Holland America's Quench ($17.95) can still stack up well if you're a soda, smoothie and specialty coffee fan. Pre-booking online almost always beats on-board prices, so check your line's site before departure.